Cutout relay system



May 3, 1949' G. L. WEBB dUTOU'I RELAY SYSTEM Original Filed Nov. 24,1944 .Zhz/enior. dear eZI. Zdefi.

Patented May 3, 1949 CUTOUT RELAY SYSTEM George L. Webb, Logansport,Ind., assignor to R-B-M Manufacturing Company,

Logansport,

Ind., a corporation of Indiana Original application November 24, 1944,Serial Divided and this application September 20, 1946, Serial No.698,351

1 Claim.

This invention relates to cutout relay systems for battery chargingcircuits, and is directed to the provision of relays suitable for usewith chargers on airplanes and other vehicles subject to severe shocksin use, while also being suitable for use with stationary chargers andin conjunction with more than one variable speed generator for charginga common storage battery. This application is a division of applicationSerial No. 564,942, filed November 24, 1944, now Patent No. 2,412,792.

With a view to causing the main contacts of a cutout or reverse currentrelay in a battery charging system to close when the generator andbattery voltages are about the same, there is provided a differentialcoil in the relay in addition to the conventional shunt and seriescoils. The differential coil is arranged to cooperate with the shunt andseries coils in controlling the position of the main contacts. It isconnected in shunt of the main contacts to be responsive to thedifference in potential between the battery and generator voltages andto the direction of said difference to assist the shunt coil in closingthe main contacts when the generator voltage is higher than the batteryvoltage, and to oppose the shunt coil and thereby oppose closing of themain contacts when the battery voltage is the higher.

By arranging to close the relay when the battery and generator voltagesare about equal, sparking of the contacts is reduced, particularly wheretwo or more genera tors are used to charge a common battery. In suchcase a cutout relay as herein described is used for each generator.

Two generators may be connected in parallel to the battery throughregulators and cutout relays employing differential coils. They can beoperated over a limited voltage tolerence range without flutter of thecircuit breaker points of the low set regulator. The instant the reversecurrent of the low set regulator exceeds its setting the circuit breakerwill open. The differential winding in the circuit breaker then comesinto play raising the closing voltage of the circuit breaker above theline voltage so that it cannot reclose until the line voltage becomeslower.

Fluttering and consequent sparking of the main contacts when they openon reverse current flow through the series coil is also reduced throughthe use of the differential coil. In such case thediiferential coilopposes the shunt coil since the' battery voltage is higher than thegenerator voltage and permits substantially free main contacts of theaction of the biasing means urging the contacts to open position.

A disadvantage of the foregoing arrangement is that the differentialcoil, being connected between the battery and the generator, provides apath over which the battery discharges through the armature of thegenerator when the latter is stopped or not generating a voltageopposing the battery voltage. It is to overcoming this disadvantage ordifficulty that the present invention is particularly addressed.

An object of this invention is to prevent battery drain through thedifferential coil of a generator cutout or reverse current relay whenthe generator is not operating.

Another object of this invention is to control the energization anddeenergization of the differential coil in accordance with the generatorvoltage.

Another object of this invention is to control the energization of thedifferential coil by a relay that, in turn, is energized in accordancewith the generator voltage.

In the drawing, the single figure illustrates a preferred embodiment ofthis invention.

It will be noted in the drawing that a shunt coil 53, differential coil55 and series coil 56 are used for controlling the operation of maincontacts, a pair of which is shown at 20 and 22. If desired a latch coiland a latch operated thereby can be used for the purpose described inthe copending application referred to hereinbefore.

In this embodiment of the invention, however, contacts 13 are providedfor controlling the energization of the differential coil 55. Thecontacts 13 may be operated by a voltage regulating relay whose coil 14is shunted across the charging generator. The coil 14 also controlscontacts 15 arranged to shunt a resistor 16 connected in the circuit ofthe field coil 11 of the generator, shown generally at 18. The armature19 of the generator 18 is connected through the coil of a currentregulating relay Whose contacts 8| are arranged to shunt resistor 82also connected in the circuit to the field coil 11. The arrangement issuch that the contacts 13 will close at a predetermined voltage belowthat at which the contacts '15 open, but will not open at the reducedvoltage caused by operation of the regulating relay contacts 8|.

It will be apparent that the energization of the differential coil 55will be controlled in the system shown in the drawing in accordance withthe charging generatorvoltage, the object being to prevent drain of thebattery 69 through the differential coil 55 when the generator 78 isstopped or not operating. The battery 69 may be arranged for charging bytwo or more generators with duplicate regulators and cutouts asspecifically described in said copending application. Such a multiplesystem has very definite advantages over known circuits. The generatorcircuit breaker will close closer to line voltage on low line voltages.This is due to the action of the differential circuit breaker Windingwhich aids the circuit breaker voltage winding causing the circuitbreaker to close below its open circuit setting. The generator willalways come on the line even though the circuit breaker open circuitsetting is above the voltage regulator setting. This is again due to theaction of the differential winding. No extra regulator terminals,contacts and external wiring are needed to obtain practical paralleloperation. The regulator with the additional windings described above isinterchangeable with present production regulators.

Since the differential coils are automatically deenergized upon droppingof the generator volago, no drain through the battery occurs when thecorresponding generator is not running. Usually one generator regulatorwill be set for a higher voltage than another. But even under thoseconditions the operation is without flutter and without battery drainagewhen each generator with its regulator and cutout is arranged as shownand described.

Since certain further changes can be made in the foregoing constructionand different embodiments of the invention can be made Without departingfrom the spirit and scope thereof, it is intended that all matter shownin the accompanying drawing or described hereinbefore shall beinterpreted as illustrative and not in a limiting sense.

What is claimed as new is:

For combination with a battery and a variable speed generator forcharging the same, a cutout relay comprising main contacts forconnecting the battery to the generator, a shunt coil disposed to beconnected for energization across the generator and to close said maincontacts when the generator voltage reaches a predetermined value, aseries coil disposed to be connected in series circuit relation with thegenerator to assist said shunt coil in holding said main contacts closedwhen current flows from the generator to the battery, a differentialcoil disposed to be connected to be responsive to the difference betweenthe battery and generator voltages and to assist said shunt coil inclosing said main contacts when the battery voltage is less than thegenerator voltage, and voltage regulating means for the generatorincluding a coil disposed to be responsive to the generator voltage,contact means for controlling the voltage of said generator, andnormally open auxiliary contacts disposed to be closed thereby when thegenerator voltage reaches a predetermined value, said auxiliary contactsbeing connected in series circuit relation with said (inferential coilfor disconnecting it from the battery when the generator is not runningto prevent drain on the battery during such time.

GEORGE L. WEBB.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 607,124 Negbauer July 12, 1898707,763 Creveling Aug. 26, 1902 2,163,502 Stewart June 20, 19392,353,268 Roberts July 11, 1944 Walley Sept. 26, 1944

